An update regarding the iPad microphone with iOS 9.3+

The Faber app updates released this week address the issue with the built-in iPad microphone input gain. In short, with the release of iOS 9.3.1, Apple chose to change the input gain range for the built-in microphone on iPad, which meant that apps such as SoundMeter needed to either adjust input gain or input sensitivity in order to continue to allow for reasonably accurate sound level measurements. Unfortunately, iOS versions 9.3.1 through 9.3.4 contain a bug that causes the previous input gain range to be applied after a microphone is connected to the headset jack and then removed.

The following Faber apps have been updated with a built-in workaround to properly apply the appropriate input gain on each version of iOS:

Each app has also been updated to support iOS 10 when it is released later this year.

iOS Audio Hardware: Stereo input via USB

If you’re looking for a way to acquire stereo input signals in apps like SignalScope Pro or IOScope, you’ll be pleased to know that you can connect a USB audio device to your iPhone, iPad, or iPod touch via Apple’s Lightning to USB Camera Adapter. Built-in USB audio support in iOS opens up a vast array of options for getting audio signals into, and out of, your iOS device. (USB audio support on iPhone and iPod touch requires iOS 7 or later.)

Compatibility

The trick is to find a device that conforms to the USB Audio Device Class specification, which essentially means that no special drivers are required when connecting the device to a host, like a Mac or an iPhone. Some device manufacturers clearly state that their product works with iOS and some do not. In general, if you find a USB audio device that does not require special drivers to work with Mac OS, then it will work with iOS as well.

Power

One thing to consider when selecting a USB audio device to connect to your iPhone or iPad is power. Some USB audio devices require an external power source, which means portability will be somewhat limited due to the need to have an A/C power outlet nearby. Other devices support USB bus power, which means they’ll draw their power from the host device (e.g. the iPhone). For portability, this would be the ideal situation since the iPhone and input device could be completely portable and operate for the life of the iPhone’s battery. However, only low-power devices can be directly powered by an iPhone or iPad, which means that a lot of otherwise compatible USB audio devices cannot be connected to iOS without some other source of power. For bus-powered USB devices that require more power, it is possible to maintain some portability with a USB battery power supply and an additional adapter cable.

A Few Examples (portable and inexpensive)

Stereo USB Audio Devices
Behringer UCA202
The UCA202 from Behringer offers very inexpensive and portable stereo input for iOS.

It features:

  • 16-bit/48 kHz sampling
  • 2 inputs and 2 outputs with RCA jacks
  • Headphone output with volume control (1/8″ jack)
  • Low power operation so it can be powered directly by an iPhone or iPad
  • S/PDIF optical digital output
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Behringer UFO202
The Behringer UFO202 is similar to the UCA202. Instead of a digital output, it offers the option to select between line-level and phono preamp input.
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ART USB Dual Pre
Another inexpensive option, which also adds mic preamps with switchable 48V phantom power, is the USB Dual Pre from ART.

It features:

  • 16-bit/48 kHz sampling
  • 2 inputs with XLR / 1/4″ combo jacks for mic preamp or line-level input
  • 2 outputs with 1/4″ jacks
  • Headphone output with volume control
  • Low power operation so it can be powered directly by an iPhone or iPad
  • Switchable 48V phantom power, powered from a 9V battery
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Adapters
Apple Lightning to USB Camera Adapter
This adapter is all that’s needed to connect a compatible USB audio device to an iPhone, iPad or iPod touch with a Lightning connector. As indicated above, if your USB device needs additional power, additional components will be needed. That will be discussed in a separate article.
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Apple iPad Camera Connection Kit
If you have an older iPhone or iPad with a 30-pin dock connector, you can connect a USB audio device with the USB adapter included in this kit. Remember that iOS 7 is required for USB audio on iPhone.
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RoomScope 4 with additional hardware support is now available for download

RoomScope 4.0 is now available for download on the App Store.

As with the recent update to IOScope, RoomScope now supports fractional octave band smoothing of 2Ch FR magnitude and coherence data (1/6, 1/12, and 1/24 octave bandwidths). RoomScope also adds built in support for iTestMic and iAudioInterface2 from Studio Six Digital and support for automatic downloading of sensitivity and frequency response data for the Dayton UMM-6 USB measurement microphone.

Other improvements to RoomScope include the following:

– RoomScope 4 employs a new plotting framework for real-time data graphs and high resolution image export.

– A bar graph is now used to display room acoustics parameters across octave or 1/3-octave frequency bands.

– Support for drawing directly to an external screen (from iPad) has been removed in favor of screen mirroring, which is handled by iOS.

– Audio hardware input and output options are now presented from a separate toolbar button, which looks like a microphone, on iPad, iPhone 6 and iPhone 6 Plus.

– It is possible to adjust the line thickness of plotted data.

Screen Shot 2015-01-19 at 1.03.05 PM

 

Screen Shot 2015-01-19 at 1.06.43 PM

Screen Shot 2015-01-19 at 1.07.08 PM

 

Screen Shot 2015-01-19 at 1.27.49 PM

 

 

Download RoomScope 4.0

 

IOScope 5 brings data overlays, spectrum smoothing, new hardware support

IOScope 5, which is now available for download on the App Store, employs a new plotting framework for real-time data graphs and high resolution image export. The new plotting capability also enables live frequency response data to be overlaid on up to 7 frequency response curves loaded from existing data files (CSV, MAT, or text data files exported from the Frequency tab in IOScope). An additional benefit is IOScope’s ability to smooth frequency response data into fractional octave bands (1/6, 1/12, and 1/24 octave bandwidths).

Screen Shot 2015-01-07 at 11.14.38 AM copy

Other additions to the new version of IOScope include:

– Built in support for iTestMic and iAudioInterface2 from Studio Six Digital.

– Built-in support for automatic downloading of sensitivity data for the Dayton UMM-6 USB measurement microphone.

– Support for drawing directly to an external screen (from iPad) has been removed in favor of screen mirroring, which is handled by iOS.

– Audio hardware input and output options are now presented from a separate toolbar button, which looks like a microphone, on iPad, iPhone 6 and iPhone 6 Plus.

– It is possible to adjust the line thickness of live and loaded frequency response data. The opacity of loaded data can also be adjusted in order to make the live data stand out in the graph.

Screen Shot 2015-01-07 at 11.15.09 AM copy

IOScope brings two-channel transfer function and impulse response analysis to iOS.

With IOScope, measure loudspeaker impedance, frequency response, and sensitivity. Measure a room impulse response. Tune a large sound reinforcement system, time-align a set of surround sound speakers, or optimize your home stereo. Determine the actual cutoff frequencies of your latest speaker crossover circuit, or teach your students the fundamentals of Fourier analysis of dynamic systems.

Measure frequency response magnitude and phase, coherence, and group delay. Time domain functions enable you to measure impulse response and auto/cross-correlation. IOScope includes a built-in signal generator for producing suitable excitation signals to analyze your system or device under test (DUT). The reference signal can be taken from the internal signal generator or from an external source (when using an external reference, a stereo or multi-channel audio input device, connected to the dock connector, is required).

Download IOScope 5 on the App Store.

IOScope 3.0 Updated for iOS 7

As in recent updates to SignalScope Pro and SoundMeter, IOScope’s appearance has been completely revamped for iOS 7. IOScope supports both iOS 6 and iOS 7, but looks largely the same on iOS 6 as the previous version.

Also new in version 3:

– Audio data handling is more efficient.

– For devices that support input gain adjustment on the built-in or headset microphone, the input gain is stored with exported data.

– When entering a preferred sample rate, “48k” can be entered in the text box, as an alternative to typing out “48000.”

– Default input sensitivities have been updated, based on measurements of the iPhone 5S and 5C microphones and headset inputs.

– Cursor info text now uses a larger font.

 

IOScope Screenshot iPhone 1 IOScope Screenshot iPhone 2 IOScope Screenshot iPhone 3

IOScope Screenshot iPhone 4 IOScope Screenshot iPhone 5

 

Download IOScope 3.0

 

 

SignalScope and IOScope support sample rates up to 192 kHz

Current versions of SignalScope (3.6.2), SignalScope Pro (2.6.2), and IOScope (2.5) include advanced audio configuration options that support user selection of the audio sample rate. Using built-in iPhone and iPad audio hardware, this typically means that sample rates as low as 8 kHz can be selected. Since the iPad additionally supports external USB audio devices, via the iPad Camera Connection Kit or the Lightning to USB adapter, sample rates as high as 192 kHz can be made available with the right hardware. Which sample rates can be selected depends on values supported by the connected audio hardware.

Typical sample rates for the built-in microphone or headset input of current iOS devices include:

  • 8 kHz
  • 11025 Hz
  • 12 kHz
  • 16 kHz
  • 22.05 kHz
  • 24 kHz
  • 32 kHz
  • 44.1 kHz
  • 48 kHz

It is possible to sample audio data at up to 192 kHz, with USB devices that support it, on iPad. One such device is the Echo 2 from Echo Digital Audio, which supports sample rates of:

  • 44.1 kHz
  • 48 kHz
  • 88.2 kHz
  • 96 kHz
  • 176.4 kHz
  • 192 kHz

SignalScope, SignalScope Pro, and IOScope are all available for download on the App Store.

Download SignalScope

Download SignalScope Pro

Download IOScope

The Echo 2 is available from B&H Photo Video and from Amazon.

SignalScope Pro 192 kHz Sampling

RoomScope and IOScope measure longer IRs and use 64-bit FFTs

RoomScope 1.2 and IOScope 2.3 arrived in the iOS App Store this week. Both apps now support impulse response measurements up to 16 seconds long and use double precision (64-bit) FFTs in their measurements. The maximum measurement length is dependent on the amount of memory available on the device, so 16-second measurements are currently only supported on the iPhone 5, iPad 3, and iPad 4. The previous generation of devices, including the iPod touch 5, supports 10-second measurements, and older devices are still limited to measurement durations of 5 seconds or less.

RoomScope 1.2 also offers the following additions:

  • Center time has been added to the list of calculated acoustic parameters.
  • All parameters are now calculated in low, mid, and high frequency bands, as defined by the ISO 3382 standard.
  • The calculation of the clarity and definition parameters (C and D) compensates for the delay of the whole and 1/3-octave band filters, as described in ISO 3382.
  • Raw IR data can now be excluded or included in CSV, MAT, and TXT file data exports.

RoomScope turns your iPad, iPhone, or iPod touch into a room acoustics measurement and analysis tool. With RoomScope, you can measure a room impulse response and then calculate reverberation time, early decay time, center time, clarity, and definition, as defined in the ISO 3382 standard. RoomScope also allows you to adjust the Schroeder decay curve integration limits with the touch of your finger and plot the calculated room parameters versus whole or 1/3-octave band center frequency.

RoomScope

 

Download RoomScope 1.2

IOScope brings true dual-channel transfer function and impulse response analysis to iOS. With IOScope, measure loudspeaker impedance, frequency response, and sensitivity. Measure a room impulse response. Tune a large sound reinforcement system, time-align a set of surround sound speakers, or optimize your home stereo. Determine the actual cutoff frequencies of your latest speaker crossover circuit, or teach your students the fundamentals of Fourier analysis of dynamic systems.

Measure frequency response magnitude and phase, coherence, and group delay. Time domain functions enable you to measure impulse response and auto/cross-correlation. IOScope includes a built-in signal generator for producing suitable excitation signals to analyze your system or device under test (DUT). See http://youtube.com/faberast for a video demo of loudspeaker impedance measurement.

 

Download IOScope 2.3

 

IOScope 2.1 exports impulse responses to AIF, CAF, or WAV audio files

IOScope 2.1 is now available for download on the App Store.

IOScope room impulse response measurement

IOScope room impulse response measurement

IOScope 2 can now export normalized impulse response data to AIF, CAF, or WAV audio files. On iOS 5, or later, audio files can be previewed with IOScope or opened with other apps on the same device that can open these file formats. Of course, IOScope also allows for audio files to be transferred to a Mac or PC via iTunes File Sharing, or downloaded with a web browser via the built-in HTTP file server.

With IOScope, measure loudspeaker impedance, frequency response, and sensitivity. Measure a room impulse response. Tune a large sound reinforcement system, time-align a set of surround sound speakers, or optimize your home stereo. Determine the actual cutoff frequencies of your latest speaker crossover circuit, or teach your students the fundamentals of Fourier analysis of dynamic systems.

Measure frequency response magnitude and phase, coherence, and group delay. Time domain functions enable you to measure impulse response and auto/cross-correlation. IOScope includes a built-in signal generator for producing suitable excitation signals to analyze your system or device under test (DUT). The reference signal can be taken from the internal signal generator or from an external source (when using an external reference, a stereo audio input device, connected to the dock connector, is required).

IOScope also turns your iOS device into a platform for data acquisition, storing acquired data in CSV or tab-delimited text files, MAT-files, or images, including high-resolution PDF files, for later retrieval from your device.

What’s new in version 2.1?

  • Impulse responses can now be exported to AIFF, CAF, or WAV audio files. On iOS 5, audio files can be previewed within IOScope, or opened in other apps that support these file formats.
  • Frequency and time domain data can now be exported to CSV files, in addition to MAT-files and tab-delimited text files. CSV files can be opened directly in Numbers, or other spreadsheet apps that support it, from within IOScope.
  • The Excitation (signal generator) tab now supports the same color schemes as the analysis tools.
  • Other cosmetic improvements have been made to the user interface.

IOScope 2.1 requires iOS 4 or later, and is now available for download on the App Store for $74.99 (USD) in the Utilities category.

Learn more or download IOScope on the App Store

IOScope audio file export

IOScope audio file export

IOScope 2 adds native support for iPad and new, lower price

IOScope 2.0 is now available for download on the App Store.

IOScope room impulse response measurement

IOScope room impulse response measurement

IOScope 2 comes with a new, lower price and offers some of the same new features which were recently added to SignalScope, SignalScope Pro and SoundMeter for iOS.

With IOScope, measure loudspeaker impedance, frequency response, and sensitivity. Measure a room impulse response. Tune a large sound reinforcement system, time-align a set of surround sound speakers, or optimize your home stereo. Determine the actual cutoff frequencies of your latest speaker crossover circuit, or teach your students the fundamentals of Fourier analysis of dynamic systems.

Measure frequency response magnitude and phase, coherence, and group delay. Time domain functions enable you to measure impulse response and auto/cross-correlation. IOScope includes a built-in signal generator for producing suitable excitation signals to analyze your system or device under test (DUT). The reference signal can be taken from the internal signal generator or from an external source (when using an external reference, a stereo audio input device, connected to the dock connector, is required).

IOScope also turns your iOS device into a platform for data acquisition, storing acquired data in tab-delimited text files, MAT-files, or images, including high-resolution PDF files, for later retrieval from your device.

What’s new in version 2.0?

  • IOScope now runs natively on iPad, as well as on iPhone and iPod touch devices.
  • iPad retina display resolution is fully supported.
  • Analyzer plots can be saved to PDF files in addition to jpeg image files.
  • Data files are accessible via iTunes file sharing, in addition to the app’s built-in web server.
  • Data files, including text and PDF files, can be previewed or printed within the app or optionally opened in another compatible app.
  • Three color schemes are supported, offering black, blue, and white background colors (white may be preferred for printing results stored in PDF or jpeg images).
  • In landscape orientation, the new full-screen mode hides the toolbar and tab bar to maximize the size of the analyzer displays.
  • IOScope offers enhanced support for audio accessories, connected via the 30-pin dock connector.
  • Input gain adjustment is available for any audio input hardware that supports it.
  • Software-selectable options for the GuitarJack and GuitarJack model 2, from Sonoma Wire Works, may be adjusted directly from within IOScope.
  • IOScope now supports multi-channel USB audio devices, connected to any iPad model via the iPad Camera Connection Kit.
  • External displays are supported on iPad (up to 1920×1200 resolution on iPad 2 or 3; up to 720p on the original iPad). External display resolution is dependent on the screen resolution as well as the video output adapter connected to the iOS device.

IOScope 2.0 requires iOS 4 or later, and is now available for download on the App Store for $74.99 (USD) in the Utilities category.

Learn more or download IOScope on the App Store

IOScope impedance measurement

IOScope impedance measurement

GuitarJack Rocks 3rd Gen iPhone and iPod touch

While the GuitarJack, from Sonoma Wire Works, was obviously designed with music recording in mind, it also works well as an I/O interface for test and measurement apps, like SignalScope Pro and IOScope. The GuitarJack, and the iAudioInterface from Studio Six Digital, are the only two iPod accessories I’m aware of that properly support both line level input and output via the 30-pin dock connector of iPhone and iPod touch devices. (The Alesis ProTrack supports line-level input and output, but not both simultaneously.)

GuitarJack and iPod touch 3G

GuitarJack In Brief

  • Simultaneous stereo line-level input and output
  • Compatible with 2nd and 3rd generation iPhone and iPod touch devices (Sonoma recommends using Airplane mode when using GuitarJack with an iPhone. Also, I had success using GuitarJack with the 1st generation iPhone and the 1st generation iPod touch, although I noticed that the GuitarJack’s low frequency rolloff was worse with those devices.)
  • High-impedance input available
  • Software-programmable input gain (Currently, gain settings are only accessible from within Sonoma’s FourTrack iPhone app.)
  • Reasonably flat frequency response over the audio band
  • Built to last (Its case is metal instead of flimsy plastic, like so many other iPod accessories.)

GuitarJack Frequency Response

The following plots of GuitarJack’s frequency response were produced with IOScope running on an iPod touch 3G. It’s important to note that these measurements include the response of both the output and input circuitry.

1/4

1/4

1/4

1/8

1/8

The frequency response magnitude is down by 2.6 dB at 20 Hz, relative to 1 kHz, when working with the 1/8″ input or the 1/4″ input in Lo-Z mode. As can be seen in the plots, the Hi-Z mode produces more low-frequency rolloff than the Lo-Z mode (its response is down by about 3 dB at 40 Hz). The GuitarJack rolls off the low end more than I would like, but it’s response is still pretty good for an iPod accessory.

GuitarJack is not compatible with iPhone 4, iPad, or iPod touch 4G. Fortunately, Sonoma appears to be working on a solution for the new iOS devices with model 2.

GuitarJack is available now for $199.

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